Why this has to continue ? What a waste of energy for a result well known, it will loop back again, trolls not only destroy a good mailing list, they destroy earth by wasting energy for useless childish problems resolved 120 years ago.
Le dim. 26 janv. 2025, 20:38, Jesse Mazer <[email protected]> a écrit : > > > On Sun, Jan 26, 2025 at 12:26 PM Alan Grayson <[email protected]> > wrote: > >> >> >> On Sunday, January 26, 2025 at 10:04:54 AM UTC-7 Alan Grayson wrote: >> >> On Sunday, January 26, 2025 at 9:13:54 AM UTC-7 Jesse Mazer wrote: >> >> On Sun, Jan 26, 2025 at 1:54 AM Alan Grayson <[email protected]> wrote: >> >> On Saturday, January 25, 2025 at 11:25:53 PM UTC-7 Brent Meeker wrote: >> >> On 1/25/2025 10:13 PM, Alan Grayson wrote: >> >> On Saturday, January 25, 2025 at 9:06:18 PM UTC-7 Brent Meeker wrote: >> >> On 1/25/2025 6:34 PM, Alan Grayson wrote: >> >> On Saturday, January 25, 2025 at 6:47:22 PM UTC-7 Jesse Mazer wrote: >> >> On Sat, Jan 25, 2025 at 8:07 PM Alan Grayson <[email protected]> >> wrote: >> >> On Monday, December 9, 2024 at 2:01:28 PM UTC-7 Brent Meeker >> wrote: >> >> > >> > Nothing odd about dilation and contraction when you know its cause. >> > But what is odd is the fact that each frame sees the result >> > differently -- that the car fits in one frame, but not in the other -- >> > and you see nothing odd about that, that there's no objective reality >> > despite the symmetry. AG >> >> The facts are events in spacetime. There's an event F at which the >> front of the car is even with the exit of the garage and there's an >> event R at which the rear of the car is even with the entrance to the >> garage. If R is before F we say the car fitted in the garage. If R is >> after F we say the car did not fit. But if F and R are spacelike, then >> there is no fact of the matter about their time order. The time order >> will depend on the state of motion. >> >> Brent >> >> Jesse; it's the last two of Brent's sentences that I find ambiguous. What >> does he mean? >> >> What about them do you find ambiguous? >> >> He's just saying that if there's a spacelike separation between the >> events F and R (as there was in his numerical example), then you can find a >> frame where R happens after F (as is true in the car frame where the car >> doesn't fit), and another frame where F happens after R (as is true in the >> garage frame where the car does fit). >> >> *What does he mean by "But if F and R are spacelike, then there is no >> fact of the matter about their time order."? (What you wrote above?) * >> >> Brent writes > Yes. Just what Jesse wrote above. It means the two >> events were so close together in time and distant in space that something >> would have to travel faster than light to be at both of them. >> >> *More important I just realized that in the frame of car fitting, the >> events F and R aren't simultaneous, so how does one apply disagreement on >> simultaneity when one starts with two events which are NOT simultaneous? AG* >> >> Brent writes > That's why you should talk about events being >> spacelike...the relativistic analogue of simultaneous. >> >> *I'd like to do that. BUT if the Parking Paradox is allegedly solved by >> star**ting in the garage frame where the car fits, the pair of events >> which define fitting are not spacelike since they occur at different >> times! * >> >> You didn't read the definition of "spacelike" that I wrote above. You >> want everything fed to you in tiny bites of knowledge which you forget >> eight lines later, so the questions start all over again. >> >> Brent >> >> >> *I read it, but didn't like it. Big difference. Maybe you should stop >> trying to read my intentions. You may be smart, but reading my intentions >> is way above your pay grade. How could two events with the same time >> coordinate be referred as "so close together". Moreover, in all discussions >> of solutions to the paradox, events that are simultaneous in one frame, are >> shown not simultaneous in another frame. This being the case, the two >> events of the car fitting in garage frame are simply NOT simultaneous! >> Also, Jesse seems to be referring to different events than the ones you >> refer to. So there's a muddle IMO. As a teacher, your preferred method is >> to intimidate students. Grade now D+. AG * >> >> >> Why do you think I am referring to different events? I referred to the >> same events F and R that Brent did (F is the event of the front of the car >> coinciding with the garage exit, R is the event of the rear of the car >> coinciding with the garage entrance). >> >> If you don't like Brent's verbal explanation, I also gave you a >> mathematical definition of "spacelike separation" in two recent posts on >> the "Brent on Parking Paradox" thread at >> https://groups.google.com/g/everything-list/c/QgVdhXi3Hdc/m/KC2lIKyrDQAJ >> and >> https://groups.google.com/g/everything-list/c/QgVdhXi3Hdc/m/FF7TpbG-DQAJ >> -- "If you know the distance x and time interval t between the two >> points/events in the coordinates of any inertial frame, to say they are >> spacelike separated just means that x > ct (and an equivalent definition is >> that neither point is in the past or future light cone of the other one)". >> Since I explicitly referred to a time interval t between the two events, if >> you had paid attention to that you would have known not to say "the pair of >> events which define fitting are not spacelike since they occur at different >> times". >> >> Jesse >> >> >> *Earlier I confused spacelike with timelike, but now I am clear about >> that. I also recall your post defining spacelike for simultaneous events. I >> was confused about my reference to different events referred to by you and >> Brent. The core issue now is that we need simultaneous events in the garage >> frame where the car fits, to determine a disagreement about simultaneity >> with the car frame. Otherwise, it make no sense to speak of any >> disagreement about simultaneity.* >> >> > I think it does make sense to say that disagreement about order of > non-simultaneous events is a consequence of the relativity of simultaneity, > I explained why in the recent post at > https://groups.google.com/g/everything-list/c/gbOE5B-7a6g/m/zx1LFvELDgAJ > -- did you read it? And it is common to include disagreement about event > order in discussions of the relativity of simultaneity, as in the the > second paragraph of the "description" section of the relativity of > simultaneity wiki article at > https://en.wikipedia.org/wiki/Relativity_of_simultaneity#Description > > Anyway, this is just a linguistic issue, if you want to use a separate > phrase "relativity of event-order" you can, it only leads to a cosmetic > change to the argument--instead of saying that disagreement about fitting > is a consequence of relativity of simultaneity, one can just say > disagreement about fitting is a consequence of relativity of event-order > for the events F and R. On the other hand, if you want to think about > fitting not in terms of events F and R but just in terms of a comparison of > the length of the garage with the length of the car, then since "length" in > a given is always defined in terms of the distance between front and back > at a single moment in time in that frame, that does involve picking events > on worldlines of the front and back that are simultaneous, so the fact that > the two frames disagree on the lengths can be understood in terms of their > disagreement about simultaneity. > > >> >> *I suppose, from you pov, I did it again; referring to difference in >> times for fitting to mean non-simultaneous. Did Brent ever prove the events >> could be non-simultaneous in time, yet be spacelike? I don't think so. AG * >> > > Yes, Brent's definition of spacelike separation at > https://groups.google.com/g/everything-list/c/gbOE5B-7a6g/m/CgV9j1QQDgAJ > was "the two events were so close together in time and distant in space > that something would have to travel faster than light to be at both of > them", which is equivalent to my definition that x > ct. For example if an > event A happens on Earth today, and 2 years later another event B happens > on Alpha Centauri 4 light years away (measured in the Earth/Alpha Centauri > rest frame), something would have to travel twice the speed of light to be > at both of them, and x > ct because x = 4 light years and ct = 2 light > years. On the other hand if event B happened on Alpha Centauri 8 years > after A, the two events would be timelike separated (x < ct) and something > traveling at half the speed of light could be at both. And if event B > happened on Alpha Centauri 4 years after A, the two events would be > lightlike separated (x = ct) and something would need to travel at exactly > the speed of light to be at both events. > > Jesse > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/everything-list/CAPCWU3KFc2fGtqN%2BanEkDKPtaVu%2Bd4jiPaNZFL05HYQv8ee8jg%40mail.gmail.com > <https://groups.google.com/d/msgid/everything-list/CAPCWU3KFc2fGtqN%2BanEkDKPtaVu%2Bd4jiPaNZFL05HYQv8ee8jg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAMW2kArT41x%3DtH%3DdAdUX440pWCoMUF2V6gH%3DpLMszN6Kh6ggbQ%40mail.gmail.com.
